The loess/paleosol sequence in loess layer L1 (Malan Loess) is invesitgated in three regions of the Western Chinese Loess Plateau, Nine pedogenic layers are found n L1 and three proxy climate indices, magnetic susceptibility (MS), grain size (GS) and CaCO3 content, are measured at intervals of 0.2 kyr in order to recover records of monsoon climate variations. Time series of MS, GS and CaCO3 content document the ghigh resolution history of summer and winther monsonn climate variations over the last 75 kyr. The records show a high degree of similarity to the warm interstadials recorded in ice cores from Greenlandand the Antarctic, and with Heinrich events in the North Atlantic, during the last glacial cycle. Bond cycles are also recorded by the Chinese loess records. Overall, our results indi8cate that numerous rapid changes in climate occurred in China during the last glacial cyfcle, but that the rage of climate variations was smaller than recorded in Greenland.

Several thick last glacial loess sequences in the western part of the Chinese Loess Plateau and an eolian-colluvial sequence in the central Mongolian Plateau are used to understand how the summer and winter monsoons responded to global forcing factors during marine isotope stages MIS.4 and 3. The magnetic susceptibility data are compared with other climatic proxy data to improve the well-publicized reconstruction of the past monsoons. This study suggests that different sensitivities between the summer and winter monsoons in responding to the northern insolation resulted in transitional climates between marine isotope stages, which were characterised by cold and wet climates in the western part of Chinese Loess Plateau. After forest-steppe in MIS 5, coniferous forest emerged at the MIS 5/MIS 4 transition in cold and moist conditions. These imply that the lower latitude oceans were still capable of supplying water vapour to the continental interior, and that the Mongolian High became dominant when the northern insolation entered a stadial state MIS 4.. Coniferous forest dominated MIS 4, but thereafter deteriorated to a steppe towards the end of the MIS 4, probably because the lower latitude oceans failed to supply water vapour to the interiors. A coniferous forest emerged again at the MIS 3rMIS 2 transition after forest-steppe in MIS 3. Consequently, the southern boundary of the Gobi Desert retreated northwards during the coniferous tree-dominated periods between 73 and 60ka and between 27 and 19ka, and expanded to maxima between 60 and 50ka and between 19 and 10ka. The extent of the Gobi Desert was considerably smaller for several times around 47ka and 41ka, and 27qka. during MIS 3 than during the Holocene, and the northern boundary retreated 5 timesaround 20ka, 24ka, 29ka, 31ka, and 34ka. in just the later part of MIS 3. q1998 Elsevier Science B.V. All rights reserved.

Pollen analyses of 85 samples from the Sanjiaocheng section well along the margin of a palaeolake at the end of the Shiyang River, NW China, show that Picea and Sabina dominate the pollen assemblage. Together they reach as high as 40% 60%, with the percentage of Picea varying inversely with that of Sabina. Similar results were obtained from another section in the Shiyang River drainage. Using modern ecological habitat relationship analogues, pollen transport characteristics, and the overall pollen assemblage, we propose that both Picea and Sabina pollen were transported by the river from the mountains at the upper reaches of the Shiyang River, and that the assemblage is more indicative of changes in upland vegetation than of local conditions near the section. This interpretation is supported by pollen data derived from surface samples, water samples, and riverbed samples. Using a moisture indicator (the Picea to Sabina ratio) and calculated pollen concentrations, we identify a series of palaeoenvironmental changes during the early Holocene (10-6.3 14C kaBP).

Molecular stratigraphic analyses using GC/MS have been performed on the top section of the Jiuzhoutai loesspaleosol sequences near Lanzhou in northwest China, with a record extending from the second-last interglacial through the present interglacial. The various molecular fossils identified from the second-order loess and paleosol layers include C14-C35 n-alkanes, C8-C30 n-alkanoic acids, C12-C30 n-alkanols and C23-C33 n-alkan-2-ones. The CPI (carbon preference index) values and the ratio of C29/C31 n-alkan-2-ones display alternations between loess deposits and paleosols. They show a significant correlation with the loess magnetic susceptibility, an indicator of the East Asian summer monsoon. The observed variations of the ketone indices in relation to the change of lithology are proposed to result from microbial re-working of higher plant inputs in the paleosols.

We present the results of magnetic susceptibility, geochemical and pollen analyses of a 120-m-long core of lacustrine and fluvial sediments from the Zoige Basin, eastern Tibetan Plateau. Palaeomagnetic dating indicates that the sediment sequence spans the last ca. 800ky. The magnetic susceptibility record appears to be related to global ice volume over this period and this relationship is used to produce a tentative revised chronology for the sediment sequence. The various climate proxies show a pattern of periodic variations over the last 800ky BP. The date of 500ky BP is a significant boundary: prior to this date, the climate proxies show a pattern of more frequent variability; after 500ky BP the variations are of lower frequency and higher amplitude. The results also indicate that marine oxygen isotope stage 13 was an unusually intense interglacial in the eastern Tibetan Plateau and Chinese Loess Plateau areas.